Tohban Report 2008-11-19

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RHESSI Tohban Report, 2008-Nov-12 to 2008-Nov-19 Pascal Saint-Hilaire,

1. Solar Activity

A teeny bit of activity last week, culminating into three low-B-class flares. Otherwise very quiet. AR 11008 is disappearing on the western limb.

2. Memory Management

Up to a few days ago, SSR was generally well-behaved, ending at 0% at the end of the pass sets. It now ends at the ~5% level, due to tha fact that we are getting less passes: ~8.7/day as opposed to the usual ~10.3/day.

3. Data gaps:

1800s gap on Nov. 17th Some gaps on Nov. 18th (waiting to be replayed)

4. Cold plate 2 temperature

98.4 K. D. Smith estimates a temperature of 110 will start to severely impede the detectors. A very coarse projection establishes that, at the current rate at which it is rising, this point could be reached in 2-3 years. Another anneal will most probably be done before then.

5. IDPU Switched Current Load Anomaly

Occuring when heaters are turned on/off (about every 4s, 5% duty cycle): A couple weeks ago, the ops team noticed a notable increase in the amount of current drawn, since the last IDPU reset. After careful study, it was determined that this current was always drawn (i.e. ever since mission start), but was simply invisible to the VC1 snapshots (0.1 Hz sampling rate). Apparently, after IDPU resets, the relative phase of the VC1 snapshot-taking and the heater activations may change, leading to situations where the heater current draw may or may not appear in VC1 plots.

6. Slow decay of battery state-of-charge:

The state of charge of RHESSI's batteries at the end of each orbit has been creeping down slowly, ever since the cryocooler power was increased (by ~10 W) after the anneal. Mark and Jeremy have recommended to remedy this right away: RHESSI will be drawing more current from its solar panels at the beginning of each S/C day. This could lead to some slight S/C balancing issues, possibly requiring tweaks for the solar radius studies, as this is expected to modify the heating/cooling cycle of the solar panels during an orbit (temperature changes in the solar panels lead to their dilation or contraction, modifying the S/C spin rate due to conservation of angular momentum).

7. Next Tohban: Hugh "The Hammer" Hudson

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